Method and system for designing and producing dental prostheses and appliances

ABSTRACT

A virtual model of an intraoral cavity is provided, wherein this process is initialized by a dental clinic, and the design and manufacture of a suitable dental prosthesis for the intraoral cavity is shared between a dental lab and a service center.

CROSS-REFERENCE

This application is a continuation application of U.S. patentapplication Ser. No. 13/399,866, filed Feb. 17, 2012, which is acontinuation application of U.S. patent application Ser. No. 12/789,573,filed May 28, 2010, now U.S. Pat. No. 8,145,340, which is a continuationapplication of U.S. patent application Ser. No. 12/007,015, filed Jan.4, 2008, now U.S. Pat. No. 7,738,989, which is a continuationapplication of U.S. patent application Ser. No. 11/062,622, filed onFeb. 23, 2005, now U.S. Pat. No. 7,333,874, which claims the benefitunder 35 USC §119(e) of U.S. Provisional Application No. 60/546,946,filed Feb. 24, 2004, the entire content of each of which is hereinincorporated by reference.

FIELD OF THE INVENTION

This invention relates to methods and systems for designing andproducing dental prostheses and appliances, and to dental prostheses andappliances produced thereby. In particular, the present invention isconcerned with such systems in which a plurality of different workcenters linked to a dental clinic utilize a common 3D database each forplanning, designing and manufacturing at least parts of such prosthesesand appliances.

BACKGROUND OF THE INVENTION

A dental treatment often begins with obtaining a three-dimensional (3D)model of a patient's teeth. The model may be a physical model of thedentition or a virtual 3D computer model. The model is used to assist indesigning a dental treatment for the patient. After the treatment hasbeen designed, the model is used to design the dental prosthesis orappliance to be applied to the teeth in order to execute the treatment.Such prostheses and appliances include, for example, bridges, crowns,and orthodontic braces.

In some instances, a negative cast of the dentition is obtained at thedental clinic in which the patient is seen, and may include both arches,one arch, or part of an arch. The cast is sent to a dental laboratory,and a positive physical model of the dentition is made from the negativecast, typically by pouring plaster into the cast allowing the plaster toset. A dental treatment is then determined at the clinic using themodel, and prostheses or appliances for mounting onto the patient'steeth are designed or selected in order to execute the treatment. Theappliances are made at a laboratory and then dispatched to the clinicfor mounting onto the patient's teeth.

It is also known to obtain a 3D virtual representation of the teeth thatis used to assist in devising a dental treatment and/or to design dentalappliances. The 3D computer model may be obtained at the dental clinicusing an optical scanner to scan the teeth directly or to scan a modelof the teeth. The computer model is then used at the clinic fordesigning or selecting appropriate dental prosthesis and/or appliancesto carry out the treatment. Instructions are then sent to a dentalappliance laboratory for making the prosthesis or appliances, which aremade at the laboratory and then dispatched to the clinic.

Alternatively, a negative cast of the dentition of each jaw is obtainedat a dental clinic that is dispatched to a dental appliance laboratorywhere a 3D positive model of the patient's teeth is made from thenegative cast. The 3D model is then scanned at the laboratory so as togenerate a virtual 3D model of the patient's teeth that is used todesign appropriate dental prosthesis or appliances. The prosthesis orappliances are produced at the laboratory and then dispatched to theclinic.

U.S. Pat. No. 6,632,089 to Rubbert et al., discloses a computer-baseddental treatment planning method. A virtual 3D model of the dentition ofa patient is obtained that is used to plan a dental treatment. Obtainingthe 3D model as well as treatment planning can be performed at a dentalclinic or at a remote location such as a dental appliance laboratoryhaving access to the virtual model of the dentition. In the lattersituation, the proposed treatment plan is sent to the clinic for review,and modification or approval by the dentist, before the requisiteappliances are made at the laboratory.

SUMMARY OF THE INVENTION

The present invention provides a system and method for designing andproducing dental prostheses, such as for example crowns and bridges. Thesystem comprises at least one dental clinic and at least one dentallaboratory. The system also comprises a dental service center that is aseparate entity with respect to the dental laboratory. The servicecenter is equipped to generate a virtual 3D model (also referred toherein as a “3D numerical model”, “numerical model” “virtual model”, andthe like) of a patient's teeth from data obtained either by scanning(typically optically) the teeth directly or by scanning a physical modelof the teeth, the process being at least initiated at the dental clinic.Alternatively, the dental lab may generate the virtual model. Theservice center is also equipped to use the computer model to design adental treatment and to select or design and to manufacture dentalprostheses, or at least a part thereof. The details of the requiredprosthesis may then be sent to the clinic, and typically part of themanufacture of the prosthesis is handled by the service center. Thedental lab may also be equipped to design at least a part of theprosthesis, typically a coping, for example by first defining the finishline on the 3D model. Alternatively, the dental lab may provide aprescription to the service center for the latter to design the coping.The clinic may then send instructions to a dental laboratory and/or tothe service center, each of which is equipped to make a part of thedental prosthesis in accordance with instructions and data receivedand/or generated from any one of the dental clinic, dental lab or fromthe service center, and the manufactured prosthesis is then dispatchedto the clinic.

In a preferred embodiment, communication between the clinics,laboratories and the service center is over an electronic communicationsnetwork such as the Internet or other suitable communications mediumsuch as an intranet, local access network, public switched telephonenetwork, cable network, etc.

At least a part of the manufacturing of the prosthesis is shared betweenthe service center and one or more dental labs, according topredetermined criteria. Further, at least one of the service center andthe at least one said dental lab is adapted for designing saidprosthesis based on the 3D numerical model of the dentition, whereinsaid prosthesis comprises an inner surface and an outer surface, whereinto provide a 3D model of said prosthesis. The service center is adaptedfor manufacturing at least a first portion of said prosthesis based onsaid 3D numerical model. In particular, the service center is adaptedfor manufacturing at least an internal surface of said prosthesis,wherein said internal surface is designed for mounting onto a targetsite comprised in said dentition. The prosthesis typically comprises atleast one coping and the aforesaid internal surface is an internalsurface of said coping. At least one of the service center and the atleast one said dental lab is adapted for designing an external surfaceof said coping based on said 3D numerical model.

Preferably, the service center comprises a material removal machine fordirectly manufacturing said coping from a suitable coping material basedon the design of said internal surface and said external surface of saidcoping. Alternatively, the material removal machine may be used formanufacturing a physical model of said coping from a suitable waxmaterial or the like based on the design of said internal surface andsaid external surface of said coping. The service center and/or at leastone dental lab, and/or an external facility, comprises means forproducing a negative cast of said physical model, and means forproducing said coping from said negative model using a suitable copingmaterial.

At least one said dental lab is adapted for manufacturing at least asecond portion of said prosthesis based on said 3D numerical model. Thedental lab is adapted for manufacturing at least an external surface ofsaid prosthesis, wherein the external surface is designed for providingadequate clearance for the prosthesis relative to other teeth in saiddentition adjacent to said prosthesis. Furthermore, the external surfaceis designed for providing adequate occlusion between the prosthesisrelative to other teeth in said dentition opposite to said prosthesis.

The external portion of the prosthesis may be manufactured by a processinvolving adding at least one layer of material to a suitable coping andsubjecting the layer to a material removal operation so that the surfaceof the layer conforms to a predetermined geometry. A plurality of layersmay be sequentially formed over said coping, such that a final saidlayer conforms to the external surface required for the prosthesis.

Optionally, the fabrication of each layer, or of the layer (when theprosthesis only comprises a single layer), of the prosthesis may beperformed using traditional methods. Such traditional methods are knownin the art, and include, for example, building porcelain or any othersuitable material layer by layer, starting with a first layer laid overthe coping, and manually working these layers to fit within the spaceallowed for the prosthesis in the intra-oral cavity. To facilitate this,a physical (typically plaster or stone) model of at least a part of theintraoral cavity can be produced, typically by the service center andbased on the 3D virtual model of the teeth, and this is sent to thedental lab.

Additionally or alternatively, the fabrication of said layer or layersis at least partially automated, and at least one dental lab comprises amaterial removal machine for removing material from said layer, andsuitable scanning means for determining the topology of said layer priorto the material removing operation. Computer means are also provided forcalculating machining paths for said material removal machine, whereinsuch paths are based on the difference between said topology of saidlayer prior to the material removing operation and the required topologyfor the surface.

The aforementioned predetermined parameters include a dimensionalaccuracy for the manufacture of a part of said prosthesis. Inparticular, when the dimensional accuracy for the manufacture of aparticular part is required to be about 40 microns or less than 40microns, for example the internal surface of the coping, the part ismanufactured by said service center. Alternatively, when the dimensionalaccuracy for a particular part is required to be within substantiallymore than 40 microns, for example an external part of the crown, thispart is manufactured by a dental lab.

In one particular application of the invention, a scan of the intraoralcavity is taken at a dental clinic, and the virtual model data thusobtained is sent to a dental lab. Then, the dental lab defines themargin line of the preparation (in the virtual model) and designs thecoping geometry. Alternatively, the virtual model is (also) sent to theservice center, together with a suitable prescription from the dentallab, in which case the service center defines the margin line of thepreparation (in the virtual model) and designs the coping geometry. Ineither case, the coping geometry is processed by the service center,which then produces a coping based on the design, either directly, orindirectly via a lost wax process, for example. The coping, togetherwith a physical positive model of the dentition, or a part thereofcomprising the preparation, is sent to the dental lab, wherein thetechnician there prepares the full prosthesis in a traditional manner,by sequentially adding one or more layers of porcelain or other suitablematerial to the coping, and shaping the layers to produce the outer formof the prosthesis, checking with the physical model that the prosthesiswill fit in the space left for it and provide adequate occlusion. Theprosthesis is then sent to the dental clinic to be fitted to thepatient.

Full flexibility in communication between the clinics, laboratories andthe service center is provided, enabling for example, many differentcommunications to be performed therebetween, including the followingnon-limiting illustrative examples:

(i) scanned data of the intraoral cavity (from which a virtual modelthereof is generated) is sent from the dental clinic to the dental laband/or service center;

(ii) 3D numerical data (i.e., the virtual model) of the intraoralcavity, created directly at the dental lab or service center, orindirectly from data transmitted to either location, is transmitted tothe dental clinic for approval;

(iii) approved 3D numerical data of the intraoral cavity, wherevercreated, is transmitted to the dental lab and/or to the service center;

(iv) definition of the margin line by means of the dental lab or theservice center is sent to the dental clinic for approval;

(v) approved margin line definition is sent to the service center and/ordental lab from the dental clinic;

(vi) definition of the 3D coping geometry by means of the dental lab orthe service center is sent to the dental clinic for approval;

(vii) approved 3D coping geometry, and/or approval thereof, is sent tothe service center and/or dental lab from the dental clinic;

(viii) prescription for the coping is sent from the dental lab to thedental clinic for approval, and approved prescription is sent to dentallab and/or service center.

Herein, “dental clinic” refers to the interface between a dentalpractitioner and a patient, and thus includes any physical entity, inparticular a clinic, in which there is interaction between a dentalpatient and a dental practitioner. While “dental practitioner” typicallyrefers to a dentist, doctor, prosthodontist or orthodontist, it alsoincludes herein all other caregivers that may interact with a dentalpatient during the course of a dental treatment. While “dental patient”typically refers to a person requiring the dental services of a dentalpractitioner, it also includes herein any person regarding whom it isdesired to create a 3D numerical model of the intra oral cavity thereof,for example for the purpose of practicing the same or for carrying outresearch.

The term “prosthesis” is herein taken to include any restoration and anyonlays, such as crowns and bridges, for example, and inlays, such ascaps, for example, and any other artificial partial or complete denture.

The terms virtual model, 3D numerical model, and the like, are usedinterchangeably herein to refer to a computer simulation of a surface,comprising 3D topographic data referring to the surface, such a surfacetypically being dental surfaces of the intraoral cavity.

In another aspect of the invention a system and method are provided fordesigning and producing dental appliances, such as for example braces.The system comprises at least one dental clinic and at least one dentallaboratory. The system also comprises a dental service center that isseparate from the dental laboratory. The service center is equipped togenerate a virtual 3D model of a patient's teeth from data obtainedeither by optically scanning the teeth directly or by scanning aphysical model of the teeth, the process being at least initiated at thedental clinic. Alternatively, the dental lab may generate the virtualmodel. The service center is also equipped to use the computer model todesign a dental treatment and to select or design and to manufactureappliances to carry out the treatment. The details of the treatment andof the required appliances may be then sent to the clinic. The clinicmay then send instructions to a dental laboratory which is equipped tomake at least a part of the dental appliances in accordance withinstructions received from either a dental clinic or from the servicecenter, and the appliances are then dispatched to the clinic.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 shows a dental service system for designing and producing dentalappliances in accordance with one embodiment of one aspect of theinvention;

FIG. 2 illustrates a portion of the intra oral cavity of a patientwherein it is desired to implant a prosthesis;

FIG. 3 illustrates in cross sectional view a crown prosthesis having acoping and a multiple layered cap.

FIG. 4 illustrates a service center according to the first embodiment ofthe invention.

FIG. 5 illustrates a dental lab according to the first embodiment of theinvention.

FIG. 6 illustrates a physical model of the intra-oral cavity of FIG. 2.

FIG. 7 illustrates in cross sectional view a crown prosthesis having amultiple layered construction.

FIG. 8 illustrates the insertion path of a bridge prosthesis accordingto the invention. and

FIG. 9 shows a method for designing and producing dental appliances inaccordance with a second embodiment of the invention.

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a system 10 for designing and producing dentalappliances, in accordance with the invention. The system 10 comprises adental service center 23, one or more dental clinics 22, and one or moredental labs 26. The dental clinics 22 and the dental labs 26 are linkedto each other and each to the dental service center 23 via acommunication means or network such as for example the Internet or othersuitable communications medium such as an intranet, local accessnetwork, public switched telephone network, cable network, satellitecommunication system, and the like, indicated by the cloud at 24.Optionally, it is also possible for some dental clinics 22 to be linkedto each other, and/or for some dental labs 26 to be linked to eachother, via the same one or a different one of said communication medium,for example when such dental clinics or labs form part of a commoncommercial entity. Further optionally, such interlinked dental clinics22 and/or dental labs 26 may be further linked with other entities, forexample a head clinic or head lab, comprising a centralized data base(not shown).

According to the invention, digitised three-dimensional (3D) informationW (FIG. 2) of the patient's intra-oral cavity, or part thereof, iscreated by the system, and this information is then used by the dentallabs 26 and/or the service center 23 for designing and/or manufacturinga custom dental prosthesis in an optimal and cost efficient manner.Accordingly, acquiring an accurate 3D representation of the intraoralcavity is the first step that is carried out by the system. Typically,the 3D information is obtained at the clinic 22, but this informationmay be obtained, alternatively, by one of the dental labs 26 or theservice centre 23, as described herein.

Preferably, each dental clinic 22 may provide the 3D digitized data ofthe intraoral cavity, including the dentition and associated anatomicalstructures of a patient, and thus comprises suitable equipment forscanning a patient's teeth. Such equipment may include, for example, ahand-held scanner 31 that is used by the practitioner to acquire the 3Ddata. Advantageously, a probe for determining three dimensionalstructure by confocal focusing of an array of light beams may be used,for example as manufactured under the name of PROSTHOCAD or as disclosedin WO 00/08415, the contents of which are incorporated herein byreference in their entirety. The 3D data obtained by the probe may thenbe stored in a suitable storage medium, for example a memory in acomputer workstation 32, before being sent over the communicationnetwork 24 to the dental service center 23 and/or to the dental lab 26,for further processing, as described below.

Alternatively, each clinic 22 may include equipment for obtaining anegative casting of a patient's teeth. In this case, the negative castor impression is taken of the patient's teeth, in a manner known in theart, and this negative model 33 is dispatched to one of the dental labs26 that is equipped to prepare from the negative model a positive cast34 suitable for scanning. The positive cast 34 may be scanned at thedental lab 26 by any method known in the art, including using theaforesaid probe manufactured under the name of PROSTHOCAD or asdisclosed in WO 00/08415. The 3D data is then transmitted over thenetwork 24 to the service center 23. Alternatively, the positive cast 34may be dispatched to the service center 23 by the dental clinic 22 andscanned at the service center to obtain the 3D data. Alternatively, theservice center 23 produces a positive model 34 from the negative model33 and is scanned thereat, or sent to the dental clinic 22 to be scannedthereat. Alternatively, the negative model 33 is scanned, either at thedental lab 26 or at the service center 23.

Alternatively, the negative model 33 provided by the clinic 22 is sentto the service center 23, either directly by the clinic 22, orindirectly via the dental lab 26, and a composite positive-negativemodel may be manufactured from the original negative model. Thereafter,the positive-negative model may be processed to obtain 3D digitizeddata, for example as disclosed in U.S. Pat. No. 6,099,314, assigned tothe present assignee, and the contents of which are incorporated hereinin their entirety.

Alternatively, the 3D digitized data may be obtained in any othersuitable manner, including other suitable intra oral scanningtechniques, based on optical methods, direct contact or any other means,applied directly to the patient's dentition. Alternatively, X-ray based,CT based, MRI based, or any other type of scanning of the patient or ofa positive and/or negative model of the intra-oral cavity may be used.The dimensional data may be associated with a complete dentition, or ofa partial dentition, for example such as a preparation only of the intraoral cavity.

Once the 3D digitized data is obtained, the next step is to design thedental prosthesis in question, followed by the manufacture thereof, andfinally the installation of the appliance in the oral cavity of thepatient.

The design and the manufacture of the appliance may each be carried outat the dental lab 26 or at the service centre 23, or alternatively oneor both of these activities may be shared between the two; in each casethe design and manufacture are based on the original 3D data of the oralcavity previously obtained.

The dental lab 26 comprises a laboratory, or a design or manufacturingentity that provides direct technical services to the dental clinic 22.Such services include, for example, scanning, manufacturing, analyzingthe preparation in the intra oral cavity to mark the location of thefinish line, for example, as disclosed in U.S. Ser. No. 10/623,707 andWO 04/008981, also assigned to the present assignee, and the contents ofwhich are incorporated herein in their entirety, and so on. The dentallab is characterized as being equipped or otherwise able to design partor whole appliances, and/or to partially manufacture or assemble thesame, particularly where close tolerances are relatively less critical.On the other hand, while the service center 23 is also equipped todesign part or whole appliances, and/or to fully or partiallymanufacture and/or assemble the same, it is particularly suited to doany of these activities where close or tight tolerances are in factcritical and/or difficult to achieve.

The service centre 23 is a different design and manufacturing entity tothe dental lab 26 and is thus separate thereto. However, while theservice centre 23 may be located in a different geographical zone to thedental clinic 26, for example, different countries, different cities inthe same country, different neighborhoods in the same city, or evendifferent buildings in the same neighborhood, they may also be housed inthe same building, and in any case maintain their separate functions andcapabilities, as described herein.

Typically, for any given prosthesis, the service center 23 shares atleast the manufacturing of the prosthesis with one dental lab 26according to predetermined criteria, as will be further elaboratedherein. Nevertheless, the manufacturing for a particular prosthesis mayalso be shared between the service center 23 and a number of dental labs26, each of which contributes a part of the manufacture. The sameapplies also to the design of the prosthesis, which may be executed atthe same or a different dental lab 26, and optionally also shared withthe service center 23.

The dental lab 26 is typically located in the same locality as theclinic 22 that it services, though the two may alternatively begeographically remote. Thus, the dental lab 26 and the clinic 22 that itservices may both be located in the same building or complex, or indifferent parts of the same city, or in different cities or countries.However, the dental lab 26 of the invention typically has an establishedworking relationship with the clinic 22, and thus tends to be,generally, within the same city.

In a first embodiment of the present invention, the dental appliance tobe manufactured is a prosthesis such as a crown. Referring to FIGS. 2and 3, such a crown, generally designated 100, has an internal surface120 and lower edge 130 that needs to be very precisely defined andmanufactured to match the preparation 80 and finish line 84,respectively, in the intraoral cavity 200 of a patient. Such a crowntypically comprises a cap 110 and a coping 125.

Referring to FIG. 1, the communication network 24 may also used to senda prescription from a clinic 22 and/or dental lab 26 to the servicecenter 23, and/or between the clinic 22 and the dental lab 26, forexample when the dental practitioner in the clinic 22 interacts with thedental lab 26 to finalize the prescription for the service center 23.The prescription may include instructions from a dentist at a clinic 22and/or from the dental lab 26 specifying which of the patient's teeth isto be restored, the material to be used for the restoration (forexample, the form and material of the shoulder, whether metal or ceramicshoulders are to be provided in the lingual and buccal parts of theprosthesis, and so on), the color of the required restoration, commentsabout the margin line (finish line), and so on.

While the term “preparation” refers to the stump left of the tooth thatis to be replaced by the crown and on which the crown is to be mounted,it also includes artificial stumps or other devices that may beimplanted in the intraoral cavity in such a position or in a positionthat is optimal for implanting the crown.

The cap 110, which may be formed from a plurality of layers 115,preferably needs to have a natural looking appearance, and thus thecolor and surface features of the cap 110 need to be matched to those ofthe other teeth of the intra oral cavity 20, particularly those inproximity to the site in which the crown 100 is to be implanted.Further, the dimensions of the cap have to be such as to enable thecrown to fit between the adjacent teeth 210, 220, and to provide properocclusion with the teeth 230 of the facing jaw. The manufacturingtolerances for the cap 110 are not as tight as for the inner surface120, and may be of the order of about 80 microns, which is within thecapabilities of most regular dental labs 26 that currently provide suchservices to clinics 22.

The coping 125 is made from a metal, ceramic, or other very strongmaterial, and is designed for taking the mechanical loads of the crown100 associated with the normal activity of the teeth. The inner surface120 and lower edge 130 of the coping 125 need to closely match thepreparation 80 and finish line 84, and moreover provide a reasonableinsertion path for the crown 100. Typically, the fitting tolerance forthe internal surface 120 and lower edge 130 needs to be in the order ofabout 40 microns or less, which is more demanding than for the cap 110.If the dimensional accuracy is not maintained to this tolerance level,there is a risk of infection of the remaining parts of the tooth, theinfection entering via the gap between the crown and the preparation, inparticular between the lower edge 130 and the finish line 84.Furthermore, where such tolerances are not met, the life of theprosthesis may be severely reduced. Although prior art dental labs dodesign and manufacture copings, such close tolerances are not typicallyachievable by most regular dental labs that currently provide suchservices to clinics. Accordingly, the design and manufacture of theinternal surface 120 and lower edge 130 may be advantageously carriedout according to the present invention by the service centre 23, whichhas the equipment and expertise to do so. By centralizing suchspecialized and accurate work from a number of clinics 22, the servicecenter 23 is able to carry out such work in a more cost effective andefficient manner, and generally more accurately, than the dental lab 26.

Referring to FIG. 4 in particular, the service centre 23 comprisessuitable hardware such as a server 300 that is suitably programmed toreceive the 3D data W of the oral cavity 200, as well as theprescription from the clinic 22 or from the dental lab 26, or possiblythe data and the prescription may be provided from a different one ofsaid clinic 22 or dental lab 26. Alternatively, the data W is providedby the server 300 or another computer at the service center 23 which isadapted for providing 3D data from a negative-positive model of thecavity, or by any other means, as described above. The server 300comprises suitable software to enable the 3D data corresponding to theexternal surface 82 of the preparation and finish line 84 to be isolatedfrom the rest of the 3D data W of the oral cavity 200, and this may bedone in an automated manner. Alternatively, this selection of the datamay be done interactively by specialized personnel. Thus, the server 300optionally comprises at least one monitor or other display means 310 fordisplaying the 3D data as a manipulable image 320, whereby by means of amouse 330, keyboard, voice recognition means, or any other suitable userinterface the said personnel may choose demarcation points on the image,which in his/her opinion correspond to the finish line. These points maybe marked with the help of a cursor 335 or other icon or the like on thedisplay means 310. The server 300 also has suitable software to definethe inner surface 120 according to predetermined parameters. Theseparameters take into account the geometries of the external surface 82of the preparation 80 and finish line 84, the spacing required betweenthe coping and the preparation to accommodate the adhesive or cementthat is used to provide the bond between the two, and also the insertionpath geometry, which is a function of the topology of preparation 80 aswell as of the adjacent teeth 210, 220. The server 300 also comprisessuitable software to automatically or interactively provide the externalshape of the coping 135, and thus provide a complete geometricalrepresentation or 3D data C of the coping, digitally. The externalsurface 126 of the coping 125 may be defined in any number of ways.Typically, at least a majority of the external surface 126 is displacedfrom the internal surface 120 by a uniform amount to provide anapproximately constant thickness throughout. However, the thickness ofthe coping may vary for a number of reasons. For example, it may benecessary in some cases to provide a coping that is stronger in someparts than in others, reflecting the activity that the crown 100 will beexpected to engage in—as a molar, incisor, canine and so on. Also, thepreparation may be of such a shape that in some areas relatively littleroom is left for the coping 125, while in other areas there is a widergap between the coping and the next tooth. The wider this gap is, thethicker the coping may be, while still permitting sufficient materialfor the cap 110 to be provided. In cases where the cap 110 is cementedor bonded onto the coping using an adhesive, it may be desired toprovide more adhesive between the lower edge of the coping and the caprelative to other parts between the coping and the cap. Accordingly, theouter surface 126 may be somewhat recessed close to the lower edge 130,and thus the coping may be thinner here. The additional adhesive thatmay be provided at the recess relieves some mechanical stress from thelower edge of the cap 110, which is structurally the weakest partthereof, typically, thus prolonging the life of the crown 100.

The server 300 is further adapted to provide machining instructions to asuitable material removal machine 400, based on the geometrical 3D dataC of the coping 125. Alternatively, the server 300 transmits the 3D dataC to another computer (not shown) that provides the machininginstructions to machine 400. The service center 23 further comprises asuitable manufacturing centre 500 for manufacturing a solid replicacorresponding to the 3D data C. Optionally, the manufacturing center 500comprises said machine 400, which may be adapted for producing a coping125 directly from a suitable hard material, using the machininginstructions. Any suitable machining tool may be used that is adaptedfor material removal, and may include inter alia mechanical tools suchas drills for example, laser tools such as for example laser drills orcutters, ultrasonic tools such as for example ultrasonic cutters, and soon. The machining paths and material removal characteristics of suchtools can be finely controlled, typically by a control computercomprised in or operatively connected to said machine 400. Thus, thecoping may be manufactured directly from the crown material, such as ametal for example, by means of machine 400.

Preferably, the coping is manufactured indirectly, in a manner such asdescribed for example in U.S. Ser. No. 60/459,624 or WO 2004/087000,also assigned to the present assignee, and the contents of which areincorporated herein in their entirety by reference. Essentially, aphysical model of the coping is machined from a suitable wax or similarmaterial, by a material removal process using a suitable machining tooland the machine 400, wherein the machining is computer controlled andbased on the 3D data C. Then, the wax model is transferred to a castingfacility 600, comprised in the manufacturing centre 500, oralternatively provided by a source external to the service center 23,including for example the dental lab 26, and a negative mold of the waxmodel is produced, typically by a lost-wax process. Thereafter, the moldis used for forming the coping 125, either by flowing a molten metalinto the mold and allowing solidification of the metal, or by injectingceramic powder thereinto and heating the same until the ceramic powdersinters and forms a solid integral unit, or by another suitable method.The mold may then be removed, thereby providing a coping 125 that isdimensionally faithful to the 3D data C to high dimensional accuracy,typically within 40 microns or less.

The wax-based method for producing the coping 125 has some advantagesover the direct material removal method, for example less wear andbreakage is experienced by the machining tool, and thus lowers costs.Furthermore, deformations of the tool, when a direct contact tool suchas for example a mechanical tool is used, is less likely, and thus lessdeviations from the nominal dimensions (i.e. 3D data C) of the coping125 occur than when producing a coping directly from a metal or otherhard material.

Once the coping 125 has been manufactured, the cap 110 can be bondedthereto, if manufactured separately. Alternatively, and typically, thecap 110 is manufactured already joined to the coping, as will becomeclearer herein. In either case, the external surface 111 of the cap 110needs to be defined first. The external surface 111 is such as toprovide:

(a) adequate clearance between the crown 100 and adjacent teeth 210, 220when the crown is fixed onto the corresponding preparation in theintraoral cavity 20; and

(b) adequate occlusion between the crown 100 and the teeth 230 of theopposite jaw when the crown 100 is fixed onto the correspondingpreparation in the intraoral cavity 20.

At the very least, the external surface 111 of the cap 110 is such as toprovide certain critical linear dimensions that comply with at least oneof the target width or target height of a site or location on the jaw onwhich the crown is to be fitted. The target width may include themesiodistal size of a tooth that is being replaced by the crown, and maybe defined such as to provide adequate clearance between the crown andadjacent teeth when the crown is fixed onto the correspondingpreparation in the intraoral cavity. The target height may be definedsuch as to provide adequate occlusion with the “working side” of thetooth and avoiding interfering contact between the crown and teeth ofthe opposite jaw when the crown is fixed onto the correspondingpreparation in the intraoral cavity.

An outer shape for the external surface 111 may be chosen, and this canbe accomplished in a number of ways. For example, if the original tooththat the crown 100 is replacing is still available, and the outersurface thereof is of a reasonable form, the tooth may be scanned andthe 3D data of the surface obtained. If necessary, this 3D data may beconsidered as a starting point, and the final shape of the externalsurface 111 is obtained by manipulating this data as required by thetechnician or other user that is designing the surface 111.Alternatively, if the patient has a reasonably healthy tooth on the samejaw but on the adjacent quadrant at a position corresponding to wherethe crown 110 is to be fitted, the 3D data of the surface of this toothis obtained. Optionally, this tooth may be scanned as described hereinto obtain the 3D spatial coordinates thereof, unless this data mayalready be available from the 3D data of the oral cavity 200 stored inthe server 300. Alternatively, a suitable profile for surface 111 may bechosen and obtained from a library 235 that comprises the 3D spatialprofiles of shapes or profiles of the outer surfaces of a plurality ofcrowns and teeth. If necessary the relative size and shape of thesurface 111 may be adjusted by the technician to better match the otherteeth in the jaw. Then, the chosen surface is adjusted in any suitablemanner, either manually, automatically, interactively or in any othermanner, in order that the required target dimensions of surface 111 willfit within a control volume that defines the maximum dimensions of thecap, as required to conform to the space available in the intra oralcavity 200. In particular, the control volume is chosen such as toprovide adequate clearance between the crown and adjacent teeth, andadequate occlusion with the opposite teeth, when the crown is properlyfixed onto the preparation.

The design of the external surface 111 may be executed at the servicecenter 23 or at the dental lab 26. If at the latter, and if use is madeof a library of 3D spatial profiles of shapes or profiles of the outersurfaces of a plurality of crowns and teeth, then the dental lab 26 canmake use of library 235 of the service centre 23, via communicationsnetwork 24. Alternatively, the dental lab 26 may have its own digitallibrary 135 of 3D spatial profiles of shapes or profiles of the outersurfaces of a plurality of crowns and teeth, operatively connected to alocal server 301 or other computer, as illustrated in FIG. 5, whichcomprises a suitable display 302 and user interface 303 such as a mouseand/or keyboard. The local server 301 is in any case in communicationwith the server 300 of the service center 23 and a computer 32 of thedental clinic 22 via network 24.

Optionally, and according to predetermined criteria, the details,including shape and size of each of the intermediate layers 115 can alsobe chosen or determined, such as are considered that will provide aparticular or desired visual effect, for example. Thus, it may bedecided, for example, to provide an outer layer made from an opalescentporcelain, but having a varying thickness, so that at some zones anintermediate layer will appear more reflective than at others.Similarly, an intermediate layer can be made from a suitable porcelainhaving a desired color, and the depth of this layer can also be variedto provide different hues of the color. For example, at places where thedepth of the layer 115 is greater, the layer 115 will appear a littlelighter than where the layer is shallower. This aspect of the design ofthe cap may be executed by the service center 23 or by the dental lab26.

Once the design of the cap 110 is complete, the next stage, that ofmanufacturing the cap 110 can begin. As mentioned before, there are atleast two methods for manufacturing the cap 110—as a separate item whichis then bonded to the coping 125; or together with the coping 125.

In the first method, the inner surface of the cap 110 needs to bedefined, and the design takes into account a number of parameters, suchas for example the geometry of the external surface 126 of the coping125, the spacing required between the cap 110 and the coping 125 toaccommodate the adhesive or cement that is used to provide the bondbetween the two. It should be noted that if this method is adopted, itis preferable for the shape of the external surface 126 of the coping tobe designed such as to provide an adequate insertion path geometry forthe cap 110, which is a function of the external surface 126 as well asof the adjacent teeth 210, 220. Thus, if necessary, a damaged cap may bereplaced on a coping 125 that is already cemented on the preparation 80,without having to remove the coping 125 from the preparation 80 and thusavoid possibly damaging the same. Since the 3D data of the cap 110,internally and externally is known, it is possible to manufacture areplacement cap 110 without having to rescan the oral cavity.Alternatively if the whole crown 100 were to be replaced, thepreparation area would need to be rescanned, as the geometry thereof mayhave changed as a result of removing the coping 125.

The next step is to combine the 3D data of the internal surface of thecap 110 and 3D data of the external surface 111 of the cap 110, toprovide a complete 3D digital model M of the cap. The 3D model M may bedesigned at the dental lab 26 or at the service center 26 itself, usingthe original 3D information W of the intraoral cavity 20, andparticularly the 3D model of the coping 125 that was previously created.Where this activity is executed at the dental lab 26, the correspondingdesign software in server 300 is accessed by the technician at the lab26 via the communications network 24. Alternatively, the design softwaremay be comprised in the computer 301 at the dental lab 26, and therequired data, including the 3D data C of the coping 110, may beacquired from the service center 23 via the communications network 24.The 3D model M is then converted, preferably by server 300 oralternatively by computer 301, into machining instructions E for machine400, for example. Thereafter, the cap 110 may be manufactured in any oneof a number of ways.

For example, the said machine 400, may be adapted for producing the cap110 directly from a suitable durable material, using the machininginstructions based on model M. As for the coping 125, any suitablemachining tool may be used that is adapted for material removal, and mayinclude inter alia mechanical tools such as drills for example, lasertools such as for example laser drills or cutters, ultrasonic tools suchas for example ultrasonic cutters, and so on. Preferably, the machiningpaths and material removal characteristics of such tools can be finelycontrolled, typically by a control computer operatively connected to orcomprised in machine 400.

Alternatively, the cap 110 may be manufactured indirectly, using awax-loss process similar to that described herein and in U.S. Ser. No.60/459,624, for the coping, mutatis mutandis. Thus, a physical model ofthe cap is machined from a suitable wax or similar material, by amaterial removal process using a suitable machining tool and the machine400. Then, the wax model is transferred to a casting facility, which maybe the same or a different casting facility 600, comprised in themanufacturing centre 500, or alternatively provided by a source externalto the service center 23, including for example the dental lab 26, and anegative mold of the wax model is produced, typically by a lost waxprocess. Thereafter, this mold is used for forming the cap 110, eitherby flowing a molten metal into the mold and allowing solidification ofthe metal, or by injecting ceramic powder thereinto and heating the sameuntil the ceramic powder sinters and forms a solid integral unit, or byany other suitable means. The mold may then be removed, therebyproviding a cap 110 that is dimensionally faithful to the 3D model M tohigh dimensional accuracy, typically within about 40 microns or less.

If it is required to manufacture the cap 110 from a plurality ofdifferent layers of materials, for example to provide a natural lookingappearance that matches the other teeth of the patient, this may be doneas follows. First, the 3D model M may used to design the outer shape ofthe outer surface 116 of each intermediate layer, as illustrated in FIG.3. The 3D models T, each corresponding to one intermediate layer 115,and of course including the final layer 118 are converted, typically byserver 300 or alternatively by computer 301, to material removalinstructions P which are executable by a suitable material removalmachine such as for example machine 400. Then, the innermost layer 117,i.e., the layer that is to be mounted directly to the coping 110, ismanufactured by direct material removal methods or by indirect methodssuch as a lost-wax process, similar to that described above for thewhole cap 110, mutatis mutandis. This stage of the manufacture, since itrequires high dimensional accuracy, is preferably carried out at theservice center 23. Where an indirect method is used, at least the waxmodel is manufactured at the service center 23 for the same reason.Then, successive layers 115 of material up to a final layer 118 may beadded to the inner layer 117, in a manner known in the art, and eachlayer is subjected to a material removal operation so that the externalsurface 116 thereof matches the design geometry, i.e., 3D data T. Thedimensional accuracy of the surfaces 116 can be 80 microns or less, andthat of external surface 111 of the cap 110, i.e., of the final layer118, is preferably about 80 microns, and thus, the material removaloperations for the intermediate and final layers may be advantageouslycarried out at the dental lab 26.

In the second method, the cap 110 is produced already joined with thecoping 125, i.e. starting with a workpiece comprising the coping 125.Essentially, a layer of suitable crown material is added to the coping125 in a manner known in the art, and this layer is then subjected to amaterial removal operation to provide the desired profile for theexternal surface 111, for example in a manual fashion, as is well knowin the art, or alternatively in a computer controlled manner, forexample similar to that as described above for the separate cap, mutatismutandis.

Thus, there is no need in this embodiment to define an inner surface forthe cap 110, since material is applied directly to the coping 125,automatically assuming the appropriate shape over the coping's outersurface, and therefore high dimensional accuracy between the cap 110 andcoping 125 is automatically achieved.

Where it is desired to manufacture the crown in which the cap 110comprises a plurality of layers 115 including a final layer 118, foreach layer suitable crown material may be added to the previous finishedlayer and subsequently machined or otherwise subjected to a materialremoval operation, manually or computer-aided, to provide the requiredprofile for each external surface 116 of the layers, including the outersurface 111 of the cap 110.

When the crown is fabricated in the traditional fashion at the dentallab 26, including one or more material layers built up over the copingmanufactured by the service center 23, there is less need for the outersurfaces of each layer to be precisely defined in a virtual model. Thusin such cases the technician at the dental lab 26 may design the cap 110in any suitable manner, including traditional methods or any othermethod, including manual, interactive of automated methods, or acombination of two or more thereof.

For the first and second methods described above, the material removaloperations for the innermost layer 117, intermediate layers 115 andfinal layer 118 can be performed at the dental lab 26, which comprises asuitable material removal machine 450 comprising any suitable machiningtool that is adapted for material removal, and may include inter aliamechanical tools such as drills for example, laser tools such as forexample laser drills or cutters, ultrasonic tools such as for exampleultrasonic cutters, and so on. Preferably, the machining paths andmaterial removal characteristics of such tools can be finely controlled,typically by a control computer operatively connected to or comprised inmachine 450 in which the machining instructions P, previously prepared,are stored. Alternatively, the material removal operations are carriedout in the dental lab 26 using more traditional methods. Particularlyfor this purpose, a physical positive model of the teeth, particularlyincluding the preparation and surrounding teeth including the adjacentteeth and the facing teeth of the opposite jaw, is provided to thedental lab 26, which assists the technician in fabricating the fullprosthesis. Such a physical model can be made from the virtual model Wusing any suitable method, such as for example material removal methodsincluding CNC machining methods, or using other techniques, for exampleprototyping methods, typically at the service center 23, thoughoptionally at the dental lab 26. Alternatively, and particularly if anegative model was used to obtain the virtual model in the first place,the positive model may be produced directly from the negative model in amanner known in the art.

It should be noted that when the manufacture of the external surfaces116 of the layers 117, 115 and 118 of the coping 110 is conducted in adifferent machine to that used for the manufacture of the internalsurface of the cap 110 (in the case of the first method) or of thecoping 125 (in case of the second method), proper spatial alignmentbetween the internal surface and the external surfaces of each componentmust be maintained. This may be achieved in a number of ways. Forexample, surface features such as projections 119 of a known geometryand located at a known position in inner surface 120 (or elsewhere) areincluded in the 3 model M, and thus also included in the physical coping125 that is manufactured. The projections 119 are used as referencedatums when the coping is moved to a different machine such as machine450 to continue with the manufacture of the crown. When the cap 110 ismanufactured separately from the coping 125, similar projections may beincluded in the cap 110, also serving as a reference datum for aligningthe cap 110 with respect to the coping 125. Alternatively, once thecoping 125 and mounted in the next machine, such as machine 450, theouter surface thereof is scanned by means of a suitable scanner, forexample scanner 330, and the 3D data thus obtained is used by computer301 to adjust the material removal instructions P such as to align theouter surface of the cap 110 with the coping 125.

Preferably, the material removal operations, for either the first orsecond methods, is carried out according to the method disclosed in U.S.Ser. No. 60/542,327, entitled “METHOD AND SYSTEM FOR MANUFACTURING ADENTAL PROSTHESIS”, filed on 9 Feb. 2004, also assigned to the presentassignee, and the contents of which are incorporated herein by referencethereto. Essentially, the crown 100 may be manufactured by performing amapping operation to determine the three-dimensional shape of the outersurface of the material that is to be machined to form the crown 100,either the final layer 118 or any intermediate layer 115, including theinner layer 117, and then subjecting the layer to a material removingoperation, wherein the machining paths are computer controlled on thebasis of the local differences between actual and required shape, andoptimized to reduce machining times. Alternatively, the crown 100 ismanufactured by performing a measuring operation to determine at leastsome critical dimensions of the outer surface 111 of the prosthesis,either the final layer or any intermediate layer. These measurements arethen compared to the corresponding nominal dimensions in which the crownis to be fitted, and then subjecting the layer to a material removingoperation, wherein the machining paths are computer controlled andoptimized to reduce machining times.

Accordingly, the distance between adjacent machining paths may bemaintained, for example in the order of 0.02-0.2 mm, and an optimalamount of material can be removed in each sweep without damaging theprosthesis and/or the tool. There is therefore no need to arrangemachining paths within a fictitious envelope, as these paths aredesigned to match the actual external details of the workpiece, i.e. thematerial layer before machining commences. Thus:

-   -   potential damage to the crown and/or tool by attempting to        remove too much material in one sweep, as may happen if the        material exceeds the limits of the envelope, is generally        avoided; and,    -   machining time is not wasted by passing the tool across empty        air for some portion of the machining paths, as may happen if        the material is well below the limits of the envelope.

According to this manufacturing process, then, for each layer that isadded to the coping 125 (for the said second method) or to the innermostlayer 117 (for the said first method, and thus also including theinnermost layer 117 itself):

a) actual dimensional data for at least one parameter associated withsaid layer is obtained;

b) for at least one such parameter, a comparison is made between theactual dimensional data and predetermined target dimensional data thatit is desired to conform said parameter to; and

c) the layer is then subjected to a material removal operation bysuitable machining means along machining paths which are a function ofsaid comparison, such that after said operation the parameter associatedwith the layer substantially conforms with said target dimensional data.

The parameter is preferably a geometric parameter comprising surfacecoordinates of each layer, while the target dimensional data comprisesthe numerical values of the surface coordinates of an idealized orrequired outer surface of the prosthesis. The surface coordinates ofsaid required outer surface are provided by the 3D models T.

The aforesaid actual dimensional data may comprise the actual surfacecoordinates of each layer prior to the material removal operation. Instep (a) the layer is scanned with a suitable three-dimensional surfaceprobe 330, typically comprised and used in said dental lab 26, andoperatively connected to the computer 301. Such a probe preferablyprovides a three dimensional structure based on confocal imaging.Alternatively, the actual dimensional data may be obtained using anysuitable intra oral scanning technique, based on optical methods, directcontact or any other means, applied directly to the patient's dentition.Alternatively, the data may be obtained using techniques based onscanning a positive and/or negative model of the intra oral cavity.Alternatively, X-ray based, CT based, MRI based, or any other type ofscanning of the patient or of a positive and/or negative model of theintra-oral cavity. The dimensional data may be associated with acomplete dentition, or of a partial dentition, for example such as thepreparation only, and corresponds to 3D data W.

Alternatively, the aforesaid parameter is a geometric parametercomprising at least one linear dimension of said layer. The targetdimensional data thus comprises the numerical values of at least one ofthe target width or target height of a location on the jaw on which thecrown is to be fitted. The target width may include the mesiodistal sizeof a tooth that is being replaced for example, and may be defined suchas to provide adequate clearance between the crown and adjacent teethwhen the prosthesis is fixed onto the corresponding preparation in theintraoral cavity. The target height may be defined such as to provideadequate occlusion between said prosthesis and teeth of the opposite jawwhen the prosthesis is fixed onto the corresponding preparation in theintraoral cavity.

Referring to FIG. 6, the dental clinic 26 may also be provided with aphysical model 700 of the part of the intra oral cavity of interest,namely comprising scale replicas the adjacent teeth 210, 220,preparation 80 and finish line 84, and upper teeth 230 opposite thepreparation and the adjacent teeth, shown as 210′, 220′, 80′, 84′ and230′ in this figure. The model 700 is in two parts, an upper part 710and a lower part 720 corresponding to the upper jaw and lower jaw,respectively and joined together reversibly in the correct occlusalrelationship by means of alignment pins 750. The model 700 is preferablymanufactured by the service centre 23 by any suitable means, for examplevia CNC machining of two solid blocks of a plaster or other material.The 3D data W that was originally taken from the intra oral cavity 20 isused for providing material removal instructions to machine 400, whichcan then manufacture the model 700 therefrom. The model 700 is thenshipped to the dental lab 23, and helps the technician there toundertake fitting tests of the crown 100 with respect to the preparation80′ and finish line 84′ in the model, before the finished crown 100 isfinally sent from the dental lab 26 to the clinic 22 for implantationinto the intra oral cavity 20 of the patient. Alternatively,particularly when the crown is built up on the coping using traditionalmethods, the model 700 may be used by the technician for designing andfabricating each of the successive layers of the cap, or when consistingof single layer, the design and fabrication thereof.

Alternatively, the crown may be manufactured as a monolithic item,wherein the coping as such is not included as a separate item. Thus,referring to FIG. 7, the internal surface of such a crown 100′ isrequired to fit over the preparation 80, and is thus designed andmanufactured in a similar manner to the internal surface 120 of thecoping 125 as described herein, mutatis mutandis, using direct materialremoval methods or indirect methods. Similarly, the external surface111′ is designed in a similar manner to external surface 111 of the cap110, as described herein mutatis mutandis. The manufacture of theexternal surface 111′ may be carried out at the service center 23,optionally concurrently with the manufacture of the internal surface120′ and lower edge 130′. However, it is also possible to send theunfinished crown 100′, after the internal surface 120′ and lower edge130′ thereof have been prepared by the service centre 23, to a dentallab 26, for a technician thereat to complete the manufacture of theexternal surface 111′, in a similar manner as described herein forexternal surface 111, mutatis mutandis. The crown 100′ may be made fromnumber of layers, 118′, 115′, 117′ and these may each be designed andmanufactured in a similar manner to that described for crown 100,mutatis mutandis. However, it is important for the proper spatialrelationship between the internal surface 120 and the external surface111′ to be maintained. For this purpose, the crown 100′ may be mountedonto an alignment jig before the internal surface material removaloperations begin. When the unfinished crown is shipped to the dental lab26 it is transferred together with the jig, which maintains a knownalignment with the manufacturing center 600 of the dental lab 26.Alternatively, the alignment may be achieved in other ways. For example,surface features such as projections 119′ of a known geometry andlocated at a known position in inner surface 120′ (or elsewhere) areincluded. The projections 119′ are used as reference datums when thecoping is moved to a different machine such as machine 450 to continuewith the manufacture of the crown 100′. Optionally, such an alignmentjig may comprise said model 700 of part or all of the dentition.Alternatively, once the crown 100′ is mounted in the next machine, suchas machine 450, the inner surface thereof is scanned by means of asuitable scanner, for example scanner 330, and the 3D data thus obtainedis used by computer 301 to adjust the material removal instructions suchas to align the inner surface of the crown 100′ with the outer surfacethereof.

While the design and manufacture of a crown prosthesis has beendescribed, similar methods may be employed mutatis mutandis to designand manufacture any other dental prosthesis, including bridges, forexample, and inlays, such as caps, for example, and any other artificialpartial or complete denture. However, and referring to FIG. 8, whendesigning a bridge 100″, care must be taken that the internal contactsurfaces 120″ for the abutment teeth 88″ each provide an adequateinsertion path 87″ with respect to the preparations 80″, taking intoconsideration the bridge 100″ as a whole, and thus that the two paths87″ must be substantially parallel.

While the design and manufacture of a prosthesis has been described,based on a representation of surface information, the three dimensionalentities in the oral cavity, such as for example the teeth gums and soon, and also the 3D entities that are designed by the system 10,including the coping 125 and cap 110, for example, may be describedinstead by solid representations.

In a second embodiment of the invention, the system 10 is used fororthodontical applications. The 3D data corresponding to the patient'sintra oral cavity 20 is determined as for the first embodiment, mutatismutandis. Referring to FIG. 1, the communication network 24 may alsoused to send a prescription from a clinic 22 to the service center 23.The prescription may include instructions from a dentist at a clinic 22specifying which of the patient's teeth are to be moved in a dentaltreatment, as well as the desired final teeth positions at to beattained at the conclusion of the dental treatment.

The service center 23 executes a dental treatment planning softwareprogram at a computer station 16 having a central processing unit, suchas a personal computer. The software imports the 3D digital dataindicative of the patient's teeth previously obtained, and possibly aprescription sent from one of the dental clinics 22. The softwareprocesses the 3D data to generate a 3D computer model 18 of thedentition that is displayed to a user on a monitor 20. The treatmentplanning software includes features to enable the user to manipulate themodel 18 to select or design dental appliances for the patient toexecute the treatment specified in a prescription sent from the clinic.For example, the user can select or custom design one or more dentalappliances (e.g. brackets or archwires) and apply virtual models ofthese appliances to the 3D model of the teeth. In the case oforthodontic appliances, the software may be configured to move thevirtual teeth in accordance with predetermined rules based upon theapplied appliances in order to simulate the movement of the teeth thatwould occur in an orthodontic treatment in which the appliances areapplied to the patient's actual teeth. The user then determines whetherthe selected dental or orthodontic appliances are satisfactory. If not,the user selects new appliances and repeats the process untilsatisfactory appliances are found.

When the user has determined that the selected dental appliances aresatisfactory, the user may send one or more images indicative of thepatients teeth with the selected appliances applied to the teeth to theclinic 22 and request confirmation of the selection from the dentist.Information regarding the patient and the determined appliances are thensent over the communications medium to one of the appliance servicecenters 23. The dentist may specify to which one of the dental labs 26the information is to be sent. Each dental lab includes equipment formanufacturing custom made dental appliances such as brackets, archwires,etc. The appliance service center 23 then manufactures the determinedappliances, and dispatches the appliances to the clinic 22.

FIG. 9 shows a method for designing and producing dental appliances, inaccordance with another aspect of the invention. In step 40, 3D dataindicative of a patient's dentition are acquired. As explained above,the data may be acquired either by scanning the patient's teethdirectly, or by other methods such as for example scanning a physicalmodel of the teeth. The acquired data are then transmitted to a dentalservice center (step 42). In step 44, a prescription is sent from adental clinic to the service center specifying the teeth that are to bemoved in a dental treatment, as well as the final position of the teethat the conclusion of the treatment. Then, in step 46, the service centerexecutes computer software to generate from the acquired data a virtual3D model of the patient's dentition. The virtual model is used todetermine the dental appliances that are required to execute the dentaltreatment specified in the prescription (step 48). Finally, in step 50,a list of the determined appliances is transmitted to a dental lab 26where the appliances are made.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, it should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While there has been shown and disclosed exemplary embodiments inaccordance with the invention, it will be appreciated that many changesmay be made therein without departing from the spirit of the invention.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1. A method for manufacturing a dental prosthesis, the methodcomprising: receiving three dimensional data indicative of a patient'soral cavity; generating, based on the three dimensional data, adentition model that includes a prosthesis preparation and externalsurface shape geometry of a prosthesis coupling portion of thepreparation; generating, based on the dentition model, prosthesis datacomprising three dimensional shape data of a first portion of the dentalprosthesis, the first portion being an internal part of the dentalprosthesis and including an inner surface of the dental prosthesis, thethree dimensional shape data of the first portion including apreparation coupling portion of the dental prosthesis that is configuredfor coupling the first portion of the dental prosthesis and thepreparation, the prosthesis data further comprising three dimensionalshape data of an outer surface of the first portion of the dentalprosthesis; fabricating the first portion of the dental prosthesis basedon the prosthesis data; and transmitting data for manufacture of asecond portion of the dental prosthesis, the second portion beingconfigured to couple with the first portion, the transmitted dataincluding at least one of: 1) three dimensional shape data of the outersurface of the first portion, and 2) three dimensional shape data of aninner surface of the second portion that is configured for coupling thesecond portion and the first portion.
 2. The method of claim 1, whereina dimensional accuracy used for fabricating the inner surface of thefirst portion is equal to or less than about 40 microns.
 3. The methodof claim 1, wherein a dimensional accuracy used for fabricating theinner and outer surfaces of the first portion is equal to or less thanabout 40 microns.
 4. The method of claim 1, wherein the first portioncomprises a prosthesis coping.
 5. The method of claim 1, wherein thethree dimensional data indicative of a patient's oral cavity is receivedover an electronic communication network.
 6. The method of claim 1,wherein the data for manufacture of the second portion is transmittedover an electronic communication network to a dental service lab.
 7. Themethod of claim 1, wherein the generated prosthesis data comprises threedimensional shape data of the inner surface and an outer surface of thesecond portion of the dental prosthesis.
 8. The method of claim 1,wherein the three dimensional data indicative of a patient's oral cavityis generated at a dental clinic.
 9. A method for manufacturing a dentalprosthesis, the method comprising: receiving three dimensional dataindicative of a patient's oral cavity; generating, based on the threedimensional data, a dentition model that includes a prosthesispreparation and external surface shape geometry of a prosthesis couplingportion of the preparation; generating, based on the dentition model,first portion prosthesis data comprising three dimensional shape data ofa first portion of the dental prosthesis, the first portion being aninternal part of the dental prosthesis and including an inner surface ofthe dental prosthesis, the first portion prosthesis data including threedimensional shape data of a preparation coupling portion of the dentalprosthesis that is configured for coupling the first portion of thedental prosthesis and the preparation, the first portion prosthesis datafurther comprising three dimensional shape data of an outer surface ofthe first portion of the dental prosthesis; transmitting the firstportion prosthesis data to a dental service center for manufacture ofthe first portion of the dental prosthesis; and fabricating a secondportion of the dental prosthesis, the second portion being an externalpart of the dental prosthesis and having an external surface of thedental prosthesis, the second portion of the dental prosthesis beingconfigured to couple with the first portion of the dental prosthesis.10. The method of claim 9, wherein a dimensional accuracy used forfabricating the inner surface of the first portion is equal to or lessthan about 40 microns.
 11. The method of claim 9, wherein a dimensionalaccuracy used for fabricating the inner and outer surfaces of the firstportion is equal to or less than about 40 microns.
 12. The method ofclaim 9, wherein the first portion comprises a prosthesis coping. 13.The method of claim 9, wherein the three dimensional data indicative ofa patient's oral cavity is received over an electronic communicationnetwork.
 14. The method of claim 9, wherein the prosthesis data formanufacture of the second portion is transmitted over an electroniccommunication network to a dental service lab.
 15. The method of claim9, wherein the generated prosthesis data comprises three dimensionalshape data of the inner surface and an outer surface of the secondportion of the dental prosthesis.
 16. The method of claim 9, wherein thethree dimensional data indicative of a patient's oral cavity isgenerated at a dental clinic.
 17. The method of claim 9, whereinfabricating the second portion of the dental prosthesis comprises:receiving the first portion of the dental prosthesis; and applying afirst material layer directly to the first portion.
 18. The method ofclaim 17, further comprising: obtaining three dimensional shape data ofan as-applied external surface of the first material layer; and usingthe three dimensional shape data of the first material layer as-appliedexternal surface to generate first machining paths for a materialremoval operation configured to produce a predefined desired externalsurface of the first material layer, the first machining paths beingtailored to the first material layer as-applied external surface toreduce machining times as compared to comparable machining pathssuitable for a fictitious external surface envelope for the firstmaterial layer.
 19. The method of claim 18, further comprising: applyinga second material layer directly to the first material layer; obtainingthree dimensional shape data of an as-applied external surface of thesecond material layer; and using the three dimensional shape data of thesecond material layer as-applied external surface to generate secondmachining paths for a material removal operation configured to produce apredefined desired external surface of the second material layer, thesecond machining paths being tailored to the second material layeras-applied external surface to reduce machining times as compared tocomparable machining paths suitable for a fictitious external surfaceenvelope for the second material layer.
 20. The method of claim 9,wherein fabricating the second portion of the dental prosthesiscomprises: receiving the first portion of the dental prosthesis;mounting the first portion to a holding fixture; scanning the innersurface of the first portion to generate three dimensional surface dataof the first portion inner surface; applying a first material layerdirectly to the first portion; using the three dimensional surface dataof the first portion inner surface to adjust material removalinstructions used to form an external surface of the first materiallayer to produce a desired alignment between the first material layerexternal surface and the first portion inner surface.
 21. A method formanufacturing a dental prosthesis, the method comprising: generating,based on three dimensional data of a patient's oral cavity, a dentitionmodel that includes a prosthesis preparation and external surface shapegeometry of a prosthesis coupling portion of the preparation;fabricating a first portion of a dental prosthesis based on thedentition model; and fabricating a second portion of the dentalprosthesis based on the dentition model, the second portion beingconfigured to couple with the first portion.